DVD Decoder for Dell Latitude D630

I have the computer noted in the subject. When I attempt to play a DVD, an error window tells me "Windows Media Player cannot play the DVD because a compatible DVD decoder is not installed on your computer." How do I get a free DVD encoder? From where can I download one? HELP!

I HAVE A {DELL LATITUDE D630} ND I CANT PLAYER DVD MOVIES I NEED HELP! ON HOW 2 PLAY MOVIES ND INSTALLED DVD DECODER? PLEASE CAN U SHOW ME WHERE 2 GO 2 DOWNLOAD IT 2 PLAY MOVIES ON LAPTOP...THANK U!! "2 GET IT FREE DOWNLOAD ON LAPTOP COMPATIBLE DVD DECODER 2 PLAY I WINDOW MEDIA PLAYER..."